Combine beef, egg, salt, pepper, the onion-prune mixture and the bulgur in a mixing bowl; mix thoroughly. Shape into four 3/4-inch-thick patties.

Step 5

Lightly oil the grill rack (hold a piece of oil-soaked paper towel with tongs and rub it over the grate). Grill the burgers over medium heat, turning once, until browned and cooked through, about 4 minutes per side. Warm pitas on the grill, if desired. Serve the burgers with the pitas.